Space-time Equalization with Smart Antenna and Hard Limiter Receiver

Both, adaptive antenna arrays for ISI cancellation and non-linear hard limiter receivers are well known as key technologies for high data rate low-cost receivers [1][2]. However, the combination of both technologies is a big challenge since non-linear receivers only provide phase or frequency samples. The amplitude information, which is required for the adaptation of the antenna array, is not accessible. Therefore, adaptive antenna arrays are most often applied in combination with linear receivers. In this paper we present a new very low cost receiver which combines adaptive antenna arrays and hard limiter receivers. The training of the adaptive antenna array is performed on basis of the complex channel impulse response (CIR), which is estimated only by phase samples. The performance of this approach is shown by means of simulations using a simple hard decision device and Maximum Likelihood equalization. Three decoding structures are compared: Optimum combining with hard decision, optimum combining with reduced state Viterbi equalizer and a single antenna receiver with full state Viterbi equalizer.